THE 2 NONERGODIC INSERTION CONSTANTS OF THE WATER MOLECULE IN H-BOND CHAINS AT 25-DEGREES-C AND THEIR INFLUENCE ON THE TERNARY DIAGRAMS WATER-ALCOHOL-ALKANE

Most of the time, the two O-H chemical bonds of a water molecule in th e liquid are both inserted in H-bond chains. These temporary insertion s are non-ergodic and, according to the thermodynamic of mobile disord er of Huyskens and Siegel, their influence on the Gibbs free energy G( h) is ruled by the fractions of time gamma during which the molecule e scapes from their influence and is able to evaporate. The general equa tion is: G(h) = n RT ln gamma. In water-alcohol mixtures mixed H-bond chains are formed and gamma(w) = [1 + Kw1C + Kw1Kw2 C-2], C being equa l to the sum of the concentrations C-w + C-A. On this basis equations are derived predicting the solubility of water at 25 degrees C in cycl ohexane-alcohol mixtures as a function of the concentration of the alc ohol. The insertion constants are fitted and one obtains a 6% agreemen t with the experimental values. At 25 degrees C in the primary alcohol s K-w1 approximate to 8.5 dm(3) mol(-1) and K-w2 approximate to 0.3 dm (3) mol(-1). In the secondary alcohols and the tertiary alxohols, the second insertion constant of water K-w2 is significantly higher (respe ctively 0.35 and 0.40 dm(3) mol(-1)). These values agree with other ex perimental observations and lead to a correct prediction of the peculi arities of the experimental ternary diagrams water-alcohol-cyclohexane . They explain why ethanol is miscible with water in all proportions w hereas from 1-butanol, phase demixing is observed.